Soul stone scene?

Nope, he didn't have to go and gather all the stones. His home planet had already been destroyed and he couldn't change that. 

He could simply lay on his ass and enjoy his life and rebuild for the rest of time, instead of trying to be the saviour of the world. 

You could make this criticism of nearly every character ever created.  Someone's actions are informed by who they are.  Thanos logic was that life unchecked leads to ruin, that sacrifices had to be made to value what one has.  He saw no reason to rebuild or assist because it just put off the issue for a later date.  

You can disagree with him. I do, but the idea of stating a character shouldn't be who they are because you don't like them is not a valid criticism to me.

It is criticism which goes against the villian. Thanos drives the whole plot, and he has no reason for doing so. That is what makes him a bad villain. 

Did Adolf Hitler have a reason for killing 6 million Jews that made sense to you?  What villain's motives meet your seal of approval?

His reason is he believes life left unchecked will ruin itself.  He saw it happen to his own people.  He has seen his efforts actually work. Gamora's planet is a paradise according to the movie a generation after the massacre of half the population.  

Just a quick update, since actuals are out. IW did $62.08M at the DBO, bringing its DBO total to ~$548.09M. So far it has outperformed BP by ~9.2% at the DBO. If this continues, IW would finish its DBO run with $764.4M. Which, if the FBO precentage holds up, would put its final WW total at ~$2.242B.

Of course, it looks like it's pretty obvious it won't have quite the same legs as BP, partly to do with strong competition in the coming weeks. Still, it should finish its DBO with ~$650M-$700M. This would put its WW BO at ~$1.906B-$2.053. FBO may prove to have better legs than DBO, though.

I still think it's cool that you can see both Black Panther and Infinity War at the theaters right now. A person could create their own Marvel double feature if they wanted to.

WW2 wasn't a movie that was meant to entertain millions. 

I thought Thanos was the best villain they had thus far. That's not saying a whole lot though, as pretty much every villain so far was just a copy/paste of the the hero of the movie but a bad guy.